Hello,my pc will work perfect all day then i might watch. you tube/webcam ect it will all of sudden screen goes blank. it tries to reboot but never manages to loads windows . to restart i have to shut down for min 10 mins and will start normal the computer is old running on xp i have tried re-image.no change. also updated all drivers .still the same. would shortage of memory do this .any clues as i dont know much about pc .thankyou